The mild oxidation of Shenmu char powder (SCP) with aqueous hydrogen peroxide (AHPO)-acetic anhydride (AAH) was carried out under different conditions, including volume-to-mass ratio of AAH to SCP (AAH/SCP), temperature, volume ratio of AHPO to AAH (AHPO/AAH), and time. Each reaction mixture was filtrated and then extracted with methanol to afford residue and extract. The optimal conditions were determined to be 60/1 of AAH/SCP, 50 degrees C, 2 of AHPO/AAH and 60 h based on the extract yield. The extracts from SCP oxidation after different periods of time ranging from 12 to 72 h were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and atmospheric pressure solid analysis probe/time-of-flight mass spectrometer (ASAP/TOE-MS). In total, 46 compounds were identified in the extracts by GC/MS analysis and carboxylic adds are predominant Malonic acid and succinic acid were detected in the extracts and their total mass content in the extracts is up to 56.5%. A series of long-chain alkenedioic acids or long-chain cycloalkanedioic acids with molecular formulae C29H56(CH2)(n)(COOH)(2) (n = 0-6) were detected in the extracts with ASAP/TOE-MS. (C) 2014 Elsevier B.V. All rights reserved.